1. Technical Field
This invention relates to temperature coefficient thermistors comprising semiconducting metal oxides, the resistance of which varies with temperature. The resistance may vary inversely with temperature, that is, it decreases with increasing temperature. This is the most common application, and these electronic components are known as negative temperature coefficient thermistors, or NTC's. However, this invention may also relate to positive temperature coefficient thermistors.
Thermistors are used, for example, as sensors in temperature monitors, compensators and controllers in solid-state electronic components.
2. Background Art
U.S. Pat. No. 4,786,888 to Yoneda, et al. discloses an NTC with a semiconducting thermistor element sintered between a pair of sheets of insulating ceramic. Internal electrodes are provided on both sides of the thermistor element, and are electrically connected, through the insulating ceramic, to corresponding external electrodes.
U.S. Pat. No. 4,912,450 to Yoneda, et al. discloses the method of making the NTC disclosed in the '888 Patent, above, which comprises:
1. Stacking a pair of green sheets of insulating ceramic material;
2. Interposing therebetween in predetermined areas a layer of thermistor element paste;
3. Providing an internal electrode paste;
4. Cutting the stacked sheets and paste into individual thermistor units;
5. Firing the thermistor units to sinter the insulating ceramic around the fired thermistor element and internal electrode paste; and
6. providing external electrodes for each thermistor unit.
Still, in the art there is a need for a simple, sturdy thermistor device with superior electrical and mechanical properties which can be manufactured easily and economically.